From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27FE3ECAAD8 for ; Fri, 23 Sep 2022 14:54:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230408AbiIWOyS (ORCPT ); Fri, 23 Sep 2022 10:54:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229512AbiIWOyR (ORCPT ); Fri, 23 Sep 2022 10:54:17 -0400 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [IPv6:2a0a:51c0:0:12e:520::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 05B6B12B4BF; Fri, 23 Sep 2022 07:54:13 -0700 (PDT) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1obk49-0005kN-E1; Fri, 23 Sep 2022 16:54:09 +0200 Date: Fri, 23 Sep 2022 16:54:09 +0200 From: Florian Westphal To: Uladzislau Rezki Cc: Florian Westphal , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, vbabka@suse.cz, akpm@linux-foundation.org, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, Martin Zaharinov Subject: Re: [PATCH mm] mm: fix BUG with kvzalloc+GFP_ATOMIC Message-ID: <20220923145409.GF22541@breakpoint.cc> References: <20220923103858.26729-1-fw@strlen.de> <20220923133512.GE22541@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Uladzislau Rezki wrote: > On Fri, Sep 23, 2022 at 03:35:12PM +0200, Florian Westphal wrote: > > Michal Hocko wrote: > > > On Fri 23-09-22 12:38:58, Florian Westphal wrote: > > > > Martin Zaharinov reports BUG() in mm land for 5.19.10 kernel: > > > > kernel BUG at mm/vmalloc.c:2437! > > > > invalid opcode: 0000 [#1] SMP > > > > CPU: 28 PID: 0 Comm: swapper/28 Tainted: G W O 5.19.9 #1 > > > > [..] > > > > RIP: 0010:__get_vm_area_node+0x120/0x130 > > > > __vmalloc_node_range+0x96/0x1e0 > > > > kvmalloc_node+0x92/0xb0 > > > > bucket_table_alloc.isra.0+0x47/0x140 > > > > rhashtable_try_insert+0x3a4/0x440 > > > > rhashtable_insert_slow+0x1b/0x30 > > > > [..] > > > > > > > > bucket_table_alloc uses kvzallocGPF_ATOMIC). If kmalloc fails, this now > > > > falls through to vmalloc and hits code paths that assume GFP_KERNEL. > > > > > > > > Revert the problematic change and stay with slab allocator. > > > > > > Why don't you simply fix the caller? > > > > Uh, not following? > > > > kvzalloc(GFP_ATOMIC) was perfectly fine, is this illegal again? > > > > static struct vm_struct *__get_vm_area_node(unsigned long size, > unsigned long align, unsigned long shift, unsigned long flags, > unsigned long start, unsigned long end, int node, > gfp_t gfp_mask, const void *caller) > { > struct vmap_area *va; > struct vm_struct *area; > unsigned long requested_size = size; > > BUG_ON(in_interrupt()); > ... > > > vmalloc is not supposed to be called from the IRQ context. It uses kvzalloc, not vmalloc api. Before 2018, rhashtable did use kzalloc OR kvzalloc, depending on gfp_t. Quote from 93f976b5190df327939 changelog: As of ce91f6ee5b3b ("mm: kvmalloc does not fallback to vmalloc for incompatible gfp flags") we can simplify the caller and trust kvzalloc() to just do the right thing. I fear that if this isn't allowed it will result in hard-to-spot bugs because things will work fine until a fallback to vmalloc happens. rhashtable may not be the only user of kvmalloc api that rely on ability to call it from (soft)irq.